PTL 1 describes a remote (for instance, back-end) file server (hereinafter referred to as the “core server”), and a local (for instance, front-end) file server (hereinafter referred to as the “edge server”) that is connected to the core server via a communication network.
In PTL 1, a user of the edge server reads a file into the edge server from the core server via the communication network, and updates the file read into the edge server. Subsequently, the edge server copies the updated file from the edge server to the core server, and stubs that file in the edge server. In other words, the file is migrated from the edge server to the core server. Subsequently, when the user accesses the stub (stubbed file), the edge server reads, from the core server, the file corresponding to the stub.